Roman Numeral Calculator Kata

The Romans wrote numbers using letters : I, V, X, L, C, D, M. (notice these letters have lots of straight lines and are hence easy to hack into stone tablets). In this simple kata, your task is to create a converter which takes a number and returns it's Roman Numeral representation.

Features

Convert from Number to Roman Numeral

Convert Valid Number

Given an input of an integer between 1 and 3,999, return the Roman Numeral equivalent.

Example:

Input	Output
1	I
349	CCCXLIX
3999	MMMCMXCIX

Invalid Number

Given an invalid number as the input, output Invalid Number: Roman Numerals are between 1 and 3,999

Convert from Roman Numeral to Number

Convert Valid Roman Numeral

Given an imput of a Roman Numeral between I and MMMCMXCIX, return the numerical equivalent

Example:

Input	Output
I	1
CCCXLIX	349
MMMCMXCIX	3999

Invalid Roman Numeral

Given an input of invalid characters for the Roman Numeral, output Invalid Roman Numeral: Valid characters are I, V, X, L, C, D, M

Roman Numeral Rules

• Roman numerals consist of the following letters: I, V, X, L, C, D, and M

Number	Roman Numeral
1	I
5	V
10	X
50	L
100	C
500	D
1000	M

• If a lesser numeral is put before a bigger it means subtraction of the lesser from the bigger ("IV" means four, "CM" means nine hundred)
• If the numeral is I, X or C you can't have more than three
• If the numeral is V, L or D you can't have more than one